Development of novel chemical sensor devices based on LB films from phthalocyaninato-polysiloxane polymers

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Abstract
The formation of LB films by substituted phthalocyaninato-polysiloxanes indicates a new principle in the design of LB-suitable molecules since this material lacks the amphiphilic nature which has been thought of as being the basic requirement for successful LB film production. These completely hydrophobic polymers allow for the controlled and highly reproducible deposition of ultrathin films, the structure of which is examined. The LB films show a macroscopic anisotropy which can be described as a frozen-in liquid crystalline phase of rod-like molecules. The high chemical and thermal stability as well as the interesting redox and optical properties give rise to various applications in the field of electronic and optical devices. The use of this type of polymeric LB film as membranes in field-effect transistors is a new approach in designing chemical sensors. A device is presented which is stable for months when in contact with aqueous electrolyte. By changing the pH of the electrolyte solution, a fast and nearly Nernstian response is observed without long-time drifts. Several methods for the introduction of further chemical sensitivities are discussed.